JP2019158480A - PREDICTION METHOD, PREDICTION DEVICE AND PREDICTION PROGRAM FOR SOLIDIFICATION CRACKING SUSCEPTIBILITY OF Al ALLOY - Google Patents

Abstract

To provide a method for predicting a susceptibility to solidification cracking of an Al alloy.SOLUTION: A method includes a solidification rate curvilinear decision step for finding a solidification rate curve which shows a relation between the temperature found and the solidification rate for a phase change at a temperature given from the liquid phase to the solid phase using composition of aluminum alloy that should be predicted; an area calculation step which finds a straight line that connects a first position and second position, determines the area S of a domain surrounded with a straight line and a solidification rate curve found previously, and decides upon the first position where a solidification rate of aluminum alloy is optional within the limits of 0.6-0.8 in a solidification rate curve; and a judgment step for judging that aluminum alloy with the larger area S that tends to generate a solidification crack in a position in which the crystallization of the first crystallization is completed and shows a turning point at which the slope is discontinued in the solidification rate curve by deciding the position of the earlier one when not producing a turning point in the case a solidification rate is set to 0.95 as the second position by contrast of two or more areas S determined according to the composition of two or more aluminum alloys which should be predicted to tend to generate cracks due to solidification.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a prediction method, prediction apparatus, and prediction program for solidification cracking susceptibility of an Al alloy.

  The Al alloy contains Al as a main component and includes various additive elements such as Fe, Si, Mn, Mg, Cu, and Zn. When producing an Al alloy, these additive elements may be accompanied by eutectic reactions as solute elements. When the additive elements are concentrated in the residual melt during the solidification process, the Al alloy is concentrated as the concentration progresses in the hypoeutectic region. The solidification temperature of the liquid drops. In addition, thermal stress accompanying thermal contraction acts during the cooling process, but if the solidification temperature decreases as the concentration progresses, there is a risk that cracks may occur in the solidified portion due to strain caused by thermal contraction that occurs with cooling.

  Since it is difficult to use the cast product in which such solidification cracks occur in a subsequent process, it is used after being remelted as scrap, resulting in a significant loss. Therefore, the influence of solidification cracking due to the Al alloy components and the presence or absence of solidification cracking in the casting process are considered to be important issues to be solved in the Al alloy manufacturing process.

For example, the following Patent Document 1 or Non-Patent Document 1 discloses a method for predicting the susceptibility to solidification cracking of an Al alloy.
In the technique described in Patent Document 1, it is assumed that the solidification observation region is divided into a plurality of regions, and solidification proceeds one by one, the liquidus temperature and the solid phase distribution coefficient are calculated from the liquid composition, and the solid phase distribution coefficient is calculated. A step of calculating the components of the solid phase generated in the base and the liquid phase adjacent thereto. Then, the above-described steps for calculating the solidification temperature of the liquid phase from the component composition of the adjacent liquid phase obtained in these steps and the solid phase and the liquid phase newly generated when the assumed alloy temperature falls below the solidification temperature are described above. A step of repeating the calculation.
The technique described in Patent Document 1 is considered to be a technique for determining the tendency of solidification cracking by determining the difference between the liquidus temperature and the solidus temperature in consideration of segregation using solidification simulation.

In the technique described in Non-Patent Document 1, a solid phase ratio of 0.75 to 0. 0 is a region that has a certain degree of strength, is low in strength, easily deforms, and is not replenished with melt even when the solid phase breaks. The region is set to 95, and it is defined that cracking occurs due to the difference between strain and strain rate in the solid phase region. Then, it is assumed that at the position in the casting direction on the surface of the ingot, the initial casting surface portion becomes a restraint portion, and the dendrite in the solid phase rate region contracts to cause strain and crack. In addition, in the thickness direction of the ingot surface, it is assumed that there are semi-solidified portions with different solid fractions in the solid fraction region, and the low solid fraction is constrained and the high solid fraction is cracked. .
In the technique described in Non-Patent Document 1, in consideration of the correlation between the solid phase rate and the intensity generation, the calculation of segregation, and the strain, the difference in the rate of strain generation with respect to the temperature change when the solid phase rate is 0.75 and 0.95. Is used as an indicator.

Japanese Patent Laying-Open No. 2005-062108

Makoto Morishita et al., “Method for predicting crack sensitivity of Al—Mn and Al—Mg aluminum alloys in DC casting”, Light Metal, Vol. 59, No. 8, (2009), P417 to P423.

The technique described in Patent Document 1 considers segregation using solidification simulation, obtains the difference between the liquidus temperature and the solidus temperature, and seeks the tendency of solidification cracking. However, this technique does not consider the generation of strain during solidification, and analyzes based only on temperature information. Therefore, there is a problem that the detection sensitivity of occurrence of solidification cracks cannot be increased.
The technique described in Non-Patent Document 1 is considered to improve the prediction accuracy by considering the correlation between the solid phase ratio and the intensity generation, the calculation of segregation, and the influence of strain. As a result of research on the casting of aluminum alloys, it has been recognized that even with the technique of Non-Patent Document 1, it is not possible to sufficiently grasp the occurrence of cracks during casting.
Al alloys have many opportunities to cast alloys with a new composition by adding various additive elements according to various demands. Al alloys with new composition ratios are easily cracked before casting, or alloys that are difficult to crack. It is thought that it is an important subject to be able to grasp the direction of whether or not.

  In view of these backgrounds, the present invention aims to provide a method for predicting susceptibility to solidification cracking with a higher accuracy than ever, and a method for producing an Al alloy with improved susceptibility to solidification cracking, even for an Al alloy having a new composition. To do. Another object of the present invention is to provide a device capable of predicting solidification cracking susceptibility and a solidification cracking sensitivity prediction program even for an Al alloy having a new composition.

(1) The method for predicting the susceptibility to solidification cracking of an Al alloy according to the present invention is a method for predicting the ease of occurrence of cracks during solidification of a plurality of Al alloys according to the composition. A solidification rate curve formulation step for obtaining a solidification rate curve indicating a relationship between the obtained temperature and a solidification rate, and determining the phase change at each temperature from the liquid phase to the solid phase, and the Al alloy in the solidification rate curve The arbitrary solid position within the range of 0.6 to 0.8 is determined, and the primary crystallization is finished, and the solidification rate curve has a discontinuous change point. If the change point does not occur, the earlier position when the coagulation rate is 0.95 is defined as the second position, and a straight line connecting the first position and the second position is obtained, An area calculating step for determining an area S of a region surrounded by the straight line and the previously determined solidification rate curve; A judgment step of judging that the Al alloy having the larger area S is more likely to cause solidification cracks by comparing the plurality of areas S determined according to the composition of the plurality of Al alloys to be predicted. And

(2) In the method for predicting the susceptibility to solidification cracking of an Al alloy according to the present invention, based on a thermodynamic database showing the relationship between temperature and solid phase rate, solidification is calculated from the liquid phase using the Scheil-Gulliver segregation model. The solidification curve formulation step is performed based on the method of calculating the phase change for each temperature up to the phase, the solidification curve formulation step is performed based on the measurement result by the differential scanning calorimeter, or based on the differential thermal analysis result The solidification curve formulation step can be performed.
(3) In the method for predicting susceptibility to solidification cracking of an Al alloy according to the present invention, the area S is an addition of a difference between a function fd indicating a solidification rate according to a thermodynamic database and a function fl indicating the straight line. And fl is a function of the temperature T, where the temperature at the solidification rate of 0.6 to _0.8 is T _0.6 to _0.8 , and the temperature at the end of primary crystal crystallization is Te. It is preferable to have a formula relationship.

(4) In the method for predicting susceptibility to solidification cracking of an Al alloy according to the present invention, the Al alloy is Si: 0.0001-3.3%, Fe: 0.0001-2.0%, Cu: 0.0001-10.0%, Mn: 0.0001-10.0%, Mg: 0.0001-10.0%, Cr: 0.0001-1.0%, Zn: 0.0001-10. 0%, Ti: 0.0001-1.0%, Ni: 0.0001-1.5%, Li: 0.0001-5.0%, Zr: 0.0001-1.0%, B: 0 One or more of 0.0001 to 1.0%, Pb: 0.0001 to 0.5%, Bi: 0.0001 to 0.5%, and V: 0.0001 to 0.5%. Al alloy containing the balance Al and inevitable impurities, and the volume fraction of the α phase of the solidified Al alloy being 80% or more is suitable. It can be.

(5) The prediction device for solidification cracking susceptibility of an Al alloy according to the present invention is a device for predicting the ease of occurrence of cracking during solidification of a plurality of Al alloys according to the composition, and is an Al alloy to be predicted A solidification rate curve formulating means for obtaining a solidification rate curve indicating a relationship between the obtained temperature and a solidification rate, and determining the phase change at each temperature from the liquid phase to the solid phase, and the Al alloy in the solidification rate curve The arbitrary solid position within the range of 0.6 to 0.8 is determined, and the primary crystallization is finished, and the solidification rate curve has a discontinuous change point. If the change point does not occur, the earlier position when the coagulation rate is 0.95 is defined as the second position, and a straight line connecting the first position and the second position is obtained, An area calculating means for determining an area S of a region surrounded by the straight line and the previously determined solidification rate curve; And determining means for determining that the Al alloy having a larger area S is more likely to cause solidification cracks, by comparing the plurality of areas S determined according to the composition of the plurality of power Al alloys. .

(6) In the prediction device for the susceptibility to solidification cracking of an Al alloy according to the present invention, the solidification curve formulation means is based on a thermodynamic database showing the relationship between temperature and solid fraction, and is based on a Scheil-Gulliver segregation model Is preferably a means for calculating the phase change at each temperature from the liquid phase to the solid phase.
(7) In the prediction device for solidification cracking susceptibility of an Al alloy according to the present invention, the area S is an addition of a difference between a function fd indicating a solidification rate according to a thermodynamic database and a function fl indicating the straight line, and the fd And fl is a function of the temperature T, where the temperature at the solidification rate of 0.6 to _0.8 is T _0.6 to _0.8 , and the temperature at the end of primary crystal crystallization is Te. It is preferable to have a formula relationship.

(8) In the prediction device for solidification cracking susceptibility of an Al alloy according to the present invention, the Al alloy is Si: 0.0001-3.3%, Fe: 0.0001-2.0%, Cu: 0.0001-10.0%, Mn: 0.0001-10.0%, Mg: 0.0001-10.0%, Cr: 0.0001-1.0%, Zn: 0.0001-10. 0%, Ti: 0.0001-1.0%, Ni: 0.0001-1.5%, Li: 0.0001-5.0%, Zr: 0.0001-1.0%, B: 0 One or more of 0.0001 to 1.0%, Pb: 0.0001 to 0.5%, Bi: 0.0001 to 0.5%, and V: 0.0001 to 0.5%. Al alloy containing the balance Al and inevitable impurities, and the volume fraction of the α phase of the solidified Al alloy being 80% or more is suitable. It can be.

(9) A prediction program for susceptibility to solidification cracking of an Al alloy according to the present invention is a program for predicting the ease of occurrence of cracks during solidification of a plurality of Al alloys according to the composition,
Using the composition of the Al alloy to be predicted, the phase change for each temperature from the liquid phase to the solid phase is obtained, and a solidification rate curve formulation means for obtaining a solidification rate curve indicating the relationship between the obtained temperature and the solidification rate;
In the solidification rate curve, an arbitrary first position is established within the solidification rate of the Al alloy within the range of 0.6 to 0.8, and the crystallization of the primary crystal is completed, and the gradient of the solidification rate curve has the gradient. The position indicating the discontinuous change point, or if the change point does not occur, the earlier position when the coagulation rate becomes 0.95 is determined as the second position, and the first position and the second position are determined. An area calculation means for obtaining an area S of a region surrounded by the straight line and the solidification rate curve obtained previously, and the plurality of the plurality of pieces obtained according to the compositions of the plurality of Al alloys to be predicted. By comparing the area S, the Al alloy having the larger area S functions as a determination unit that determines that solidification cracking is likely to occur.

(10) In the prediction program for the susceptibility to solidification cracking of an Al alloy according to the present invention, the solidification curve formulation means is based on a thermodynamic database showing the relationship between temperature and solid fraction, and is based on a Scheil-Gulliver segregation model Is preferably a means for calculating the phase change at each temperature from the liquid phase to the solid phase.
(11) In the prediction program for susceptibility to solidification cracking of an Al alloy according to the present invention, the area S is an addition of a difference between a function fd indicating a solidification rate according to a thermodynamic database and a function fl indicating the straight line. And fl is a function of the temperature T, where the temperature at the solidification rate of 0.6 to _0.8 is T _0.6 to _0.8 , and the temperature at the end of primary crystal crystallization is Te. It is preferable to have a formula relationship.

(12) In the prediction program for solidification cracking susceptibility of an Al alloy according to the present invention, the Al alloy is Si: 0.0001-3.3%, Fe: 0.0001-2.0%, Cu: 0.0001-10.0%, Mn: 0.0001-10.0%, Mg: 0.0001-10.0%, Cr: 0.0001-1.0%, Zn: 0.0001-10. 0%, Ti: 0.0001-1.0%, Ni: 0.0001-1.5%, Li: 0.0001-5.0%, Zr: 0.0001-1.0%, B: 0 One or more of 0.0001 to 1.0%, Pb: 0.0001 to 0.5%, Bi: 0.0001 to 0.5%, and V: 0.0001 to 0.5%. Including the remaining Al and inevitable impurities, the volume fraction of the α phase of the Al alloy after solidification is 80% or more It can be applied to the gold.

According to the present invention, in the solidification rate curve, the first position between the solidification rates of 0.6 to 0.8 and the gradient of the solidification rate curve at the end of crystallization of the primary crystal are discontinuous change points. A straight line connecting the second position of 0.95 was formulated, the area S surrounded by the solidification rate curve and the straight line was calculated, and the compared Al alloys were compared by comparing the size of the area S between the Al alloys to be compared. It can be predicted that an alloy having a large area S is likely to cause solidification cracking.
In the Al alloy, the first position is a position where the strength at the time of solidification starts, and the integral value of the non-linearity of the latent heat generation between the first position and the second position is easy to crack when the Al alloy is solidified. It is considered to be an indicator of
When the Al alloy is cooled at a constant cooling rate, thermal stress due to cooling does not occur, whether it is fast or slow, but the integrated value of the deviation from the linear difference due to latent heat generation is the cause of strain that causes solidification cracking. By comparing the integrated value of this deviation, that is, the size of the area S, the easiness of cracking of the Al alloy can be compared.

Schematic which shows an example of the state which casts the ingot of Al alloy with a vertical semi-continuous casting apparatus. The flowchart which shows the flow of the prediction method of the solidification cracking sensitivity which concerns on 1st Embodiment of this invention. The flowchart which shows the flow in the case of calculating the area S by formulating the solidification rate curve by applying the physical property value calculation software of the multicomponent alloy in the flow of the first embodiment. The block diagram which shows one Embodiment of the prediction apparatus of the solidification crack sensitivity which concerns on 1st Embodiment, and the prediction program of solidification crack sensitivity. The graph which shows an example which formulated the solidification rate curve of Al alloy of a specific composition using the physical-property-value calculation software of a multicomponent system alloy in an Example. The graph which shows an example of the relationship between the solidification rate and temperature obtained when formulating the solidification rate curve of Al alloy using the physical property value calculation software of the multicomponent alloy. The graph which shows an example when a singular point arises in the coagulation rate 0.95 vicinity in the coagulation rate curve. The graph which expands and shows the part of the same singularity. It is explanatory drawing for demonstrating the process which calculates an example of the numerical sequence obtained by exposing the data which calculated the solidification rate curve to spreadsheet software, the temperature range, and the inclination of a solidification rate curve, (A) is 700-682 degreeC. The figure which shows the numerical value of the row | line | column of the temperature row | line | column, the row | line | column of gradient in 0.75, the row | line | column of difference of 0.75, the row | line | column of a linear y coordinate, and the dt row | line | column of a nonlinear difference, (B) (C) is a figure which shows the numerical value of the same row in 558-548 degreeC, (D) is T1, T2, R1, R2, T1-T2, R1-R2, | R1-R2 | using these numerical values. The figure which shows the numerical value of the result of calculating values, such as / dt. The graph which contrasts and shows the solidification rate curve of each Al alloy computed using physical property value calculation software about Al alloy of a some composition. Explanatory drawing which compares and shows the result of having calculated area S from the contrast of the solidification rate curve of each alloy shown in FIG. In each Al alloy shown in FIG. 10, a graph showing the relationship between strain rate difference and [Delta] T _II in the region II of the coagulation rate 0.75 to 0.95. The graph which shows the correction result obtained when the inclination just before crystallization is employ | adopted manually in the solidification rate curve of Al alloy applicable when the specific point shown in FIG. 7 arises.

Hereinafter, a solidification crack sensitivity prediction method, a solidification crack sensitivity prediction apparatus and a solidification crack sensitivity prediction program using the same according to the present invention will be described in detail based on embodiments shown in the accompanying drawings.
The solidification cracking susceptibility prediction method according to the first embodiment of the present invention relates to a method for predicting the difficulty of occurrence of solidification cracking seen in the solidification process when an Al alloy ingot is produced by a semi-continuous casting method.
Here, before explaining the details of the method for predicting solidification cracking susceptibility according to this embodiment, FIG. 1 shows a vertical water-cooled semi-continuous casting apparatus (DC casting apparatus) used in carrying out the semi-continuous casting method. This will be described with reference to FIG.

A semi-continuous casting apparatus 1 shown in FIG. 1 includes a launder 3 in which an Al alloy melt 2 is accommodated, a nozzle 5 provided under the launder 3, and a mold provided so as to surround the lower side of the nozzle 5. 6 and a bottom block 7 movably provided in the vertical direction below the mold 6 by a hydraulic cylinder (not shown) or the like.
The mold 6 is filled with the cooling water W, and the molten water 2 is cooled by supplying the cooling water W from the discharge part 6a below the mold around the molten metal 2 moving below the mold 6. The ingot 9 can be continuously cast on the bottom block 7.
When the ingot 9 has a predetermined length, the ingot 9 having a predetermined shape and size can be obtained by stopping the injection of the molten metal 2 into the mold 6 and the lowering of the bottom block 7.
In addition, a float-type molten metal surface control system (not shown) may be provided around the tip side of the nozzle 5 to control the flow of the molten pool 10 formed above the ingot 9.

  The method for predicting the susceptibility to solidification cracking according to the present invention is such that, when performing such DC casting, for example, prior to casting the ingot 9 using an Al alloy having a new or desired composition component, the Al alloy is concerned. A method, an apparatus, and a program for predicting whether or not an ingot 9 made of is likely to be solidified and cracked are provided.

As shown in FIG. 2, the solidification cracking susceptibility prediction method according to the first embodiment of the present invention includes an input step S1, a solidification rate curve formulation step S2, an area S calculation step S3, a determination step S4, and an output step S5. , Executed based on this procedure.
Hereinafter, physical property value calculation software suitable for performing the input step S1 and the coagulation rate curve formulation step S2 will be described.
In this embodiment, the main steps of the input step S1 and the coagulation rate curve formulation step S2 are performed using JmatPro (product name), a physical property value calculation software marketed by UES Software Asia Co., Ltd. can do.

JmatPro (trade name) is widely known as software for calculating the physical, thermodynamic and mechanical properties of alloy based on temperature, cooling rate and strain rate, from its chemical components. Currently, there are a wide variety of thermodynamic database and physical property database, such as Al alloy, Mg alloy, cast iron, general steel, stainless steel, Cu alloy, Ni alloy, Ti alloy, Co alloy, solder alloy, Zr alloy, etc. Crossing.
With this physical property value calculation software (JmatPro: trade name), solidification properties (solidification rate, density, thermal conductivity, enthalpy, specific heat, viscosity) can be obtained by calculation.
This physical property value calculation software uses the CAL-HAD method (CAL-culation of PHAse Diagram), which is a well-established method for calculating the phase diagram of multi-component alloys, and calculates the Gibbs free energy of each phase depending on the alloy system. It expresses mathematically, calculates the mixed state where the energy is minimized, obtains the phase boundary, obtains the thermodynamic parameter representing the Gibbs free energy from the experiment, and registers it in the thermodynamic database.

FIG. 3 shows a flowchart of the main process from the start process to the calculation of the solidification rate when using the physical property value calculation software.
First, in step S1, an alloy component composition is input. This physical property value calculation software uses the Sheile-Gulliver (SG) model or Scheil formula for solidification calculation in step S21 based on the thermodynamic database (Thermotech database) DB1 according to the alloy composition input information. The phase change at each temperature from the liquid phase to the solid phase can be calculated in detail by linking with the CALPHAD method.
In this physical property value calculation software, when solidification is completed, the phase fraction of the solid phase formed during solidification is maintained, and the physical property values are assumed that no phase change occurs except for the iron alloy below the solid phase line. Calculate

  In this embodiment, as an Al alloy, Si: 0.0001-3.3%, Fe: 0.0001-2.0%, Cu: 0.0001-10.0%, Mn: 0.00% by mass. 0001 to 10.0%, Mg: 0.0001 to 10.0%, Cr: 0.0001 to 1.0%, Zn: 0.0001 to 10.0%, Ti: 0.0001 to 1.0% , Ni: 0.0001 to 1.5%, Li: 0.0001 to 5.0%, Zr: 0.0001 to 1.0%, B: 0.0001 to 1.0%, Pb: 0.0001 -0.5%, Bi: 0.0001-0.5%, V: One or more of 0.0001-0.5%, consisting of remaining Al and inevitable impurities, after solidification The Al alloy can be applied to an Al alloy having an α phase volume fraction of 80% or more.

The component elements of the Al alloy that can be applied to the solidification cracking sensitivity prediction method according to the first embodiment of the present invention will be described individually below. In the following description, “%” means mass%.
"Si: 0.0001-3.3%"
Si is a component that contributes to the solid solution strengthening and precipitation strengthening of Al alloys, and the content of less than 0.0001% is an inevitable impurity level, and when it exceeds 3.3%, an eutectic phase exceeding 25% is generated. However, since the solidification rate of 0.75 is all after eutectic solidification, it is difficult to apply this prediction method. The Si content is more preferably 1.68% or less when applied to a method for predicting solidification cracking sensitivity.
There is an alloy containing a relatively large amount of Si in an Al alloy. When a large amount of Si enters, the eutectic phase increases, and the solid phase ratio of strength development does not match. Specifically, if the eutectic composition is 12.6% Si, the solid solubility limit is 1.1%, the Si concentration is X%, and the liquidus in the phase diagram is approximated to a straight line, The ratio of the remaining liquid phase is (12.6-X) :( X-1.1) when X> 1.1. In the present embodiment, the range of the solid phase ratio of 0.75 to 0.95 will be discussed. However, if it exceeds 3.3% Si, the solid phase ratio immediately above the eutectic temperature is less than 0.75, and therefore used in the present invention. It becomes difficult to establish logic. When applied to the solidification cracking susceptibility prediction method of this embodiment, the Si content is more preferably in the range of 1.68% or less until eutectic is not generated up to a solid phase ratio of 0.95.

“Fe: 0.0001 to 2.0%”
Fe is a component that contributes to precipitation strengthening of the Al alloy, and the content of less than 0.0001% is an inevitable impurity level, and if it exceeds 2.0%, the strength decreases due to needle-like crystals and rolling cracks occur. The fear increases.

“Cu: 0.0001 to 10.0%”
Cu is a component that contributes to precipitation strengthening and potential adjustment of the Al alloy. Less than 0.0001% is an unavoidable impurity level, and when it exceeds 10.0%, corrosion resistance due to brittle intermetallic compound crystallization. There is a high risk of a decrease. Furthermore, since the ratio of the eutectic phase approaches 25%, it is difficult to apply this prediction method.
Although the solid solubility limit of Cu is 4.9%, the eutectic composition is 33% Cu, and the residual liquid phase that becomes eutectic is difficult to increase.

“Mn: 0.0001 to 10.0%”
Mn is a component that contributes to solid solution strengthening and precipitation strengthening of the Al alloy. Less than 0.0001% is an unavoidable impurity level, and when it exceeds 10.0%, workability deteriorates due to coarse crystals. Is likely to occur.
Although the solid solubility limit of Mn is as small as 1.82%, the eutectic composition is also 1.95%, and the problem of lowering the solid phase ratio does not occur in Mn hypoeutectic. In Mn hypereutectic, Al6Mn, which is a general equilibrium phase, crystallizes, but the crystallization temperature of Al6Mn becomes too high due to an increase in Mn. The melting point at 10.0% Mn is 800 ° C., and the melting temperature of the Al alloy is close to the limit. If the melting temperature of the Al alloy n is higher than 800 ° C., problems such as gas absorption and an increase in the amount of oxide generated are likely to occur.

“Mg: 0.0001 to 10.0%”
Mg is a component that contributes to solid solution strengthening, precipitation strengthening, and weight reduction of Al alloys. Less than 0.0001% is an unavoidable impurity level, and when it exceeds 10.0%, the melt fluidity deteriorates. There is a high risk that processability will deteriorate.
Mg, unlike Si, has a high solid solubility limit of 18.9%, and a range exceeding 10.0% is not selected for the reasons described above before an event occurs in Si.
“Cr: 0.0001 to 1.0%”
Cr is a component that contributes to solid solution strengthening and precipitation strengthening of the Al alloy, and the content of less than 0.0001% is an unavoidable impurity level. Become.

“Zn: 0.0001 to 10.0%”
Zn is a component that contributes to solid solution strengthening, precipitation strengthening, and potential adjustment of the Al alloy, and the content of less than 0.0001% is an inevitable impurity level, and when it exceeds 10.0%, workability deteriorates. The fear increases. Zn has an extremely large solid solubility limit of nearly 50%, and is unlikely to cause problems when added.
“Ti: 0.0001 to 1.0%”
Ti is a component that contributes to solid solution strengthening of the Al alloy and contributes as a finening agent. Less than 0.0001% is an inevitable impurity level, and when it contains more than 1.0%, a coarse crystallized product ( TiAl ₃ ) is generated, and there is a high risk that workability will be deteriorated, and there is a possibility that it will not be completely dissolved in the molten metal.

"Ni: 0.0001-1.5%"
Ni is a component that contributes to the solid solution strengthening and precipitation strengthening of Al alloys. Less than 0.0001% is an inevitable impurity level, and when it exceeds 1.5%, an eutectic phase exceeding 25% is generated. However, since the solidification rate of 0.75 is all after eutectic solidification, it is difficult to apply this prediction method.
"Li: 0.00001-5.0%"
Li is a component that contributes to solid solution strengthening, precipitation strengthening, and weight reduction of an Al alloy. Less than 0.00001% is an inevitable impurity level, and when it exceeds 5.0%, an oxide film is easily generated. The problem of erosion of the refractory material of the DC casting apparatus is likely to occur.

“Zr: 0.0001 to 1.0%”
Zr is a component that contributes to precipitation strengthening of the Al alloy, and if less than 0.0001% is an unavoidable impurity level, and if it exceeds 1.0%, there is a high possibility that workability will deteriorate.
“B: 0.0001 to 1.0%”
B is a component useful as a finer agent for Al alloys, and if less than 0.0001% is an unavoidable impurity level, if it exceeds 1.0%, coarse crystallized products are likely to be formed and do not dissolve in the molten metal. The fear increases.

“Pb: 0.0001 to 0.5%, Bi: 0.0001 to 0.5%”
Pb and Bi are elements that contribute to the generation of the low melting point phase of the Al alloy, and less than 0.0001% is an inevitable impurity level. In many cases, a liquid phase is easily generated when heat such as heat treatment or aging is applied, causing defects, and a low melting point phase may ooze out on the surface during casting.
“V: 0.0001 to 0.5%”
If V is less than 0.0001%, it is an inevitable impurity level, and if it exceeds 0.5%, there is a high possibility that workability will be deteriorated.

  Although it can apply to the Al alloy of the above description, as an Al alloy, Si: 0.0001-1.68%, Fe: 0.0001-1.5%, Cu: 0.00001-7. 0%, Mn: 0.0001 to 3.0%, Mg: 0.0001 to 5.0%, Cr: 0.0001 to 0.5%, Zn: 0.0001 to 8.5%, Ti: 0 .0001-0.5%, Ni: 0.0001-2.5%, Li: 0.0001-3.5%, Zr: 0.0001-0.5%, B: 0.0001-0.1 %, Pb: 0.0001 to 0.2%, Bi: 0.0001 to 0.3, V: 0.0001 to 0.25%, one or two or more of the remaining Al and inevitable impurities And is applied to an Al alloy having a volume fraction of α phase of the Al alloy after solidification of 80% or more. Masui.

  When the component composition of these applicable Al alloys is input, JmatPro (trade name) uses the Scheil-Gulliver (SG) model or Scheil model in step S22, extrapolation step S23, and each phase property value calculation step S24. Extrapolation to the solidus temperature is linked to the method, and the physical properties of each phase are calculated based on the physical property database DB2 based on the enthalpy, specific heat, latent heat, solid fraction, amount, and composition of each phase during the solidification process. In step S24, it can be calculated directly from the calculation formula. The physical property value database DB2 here is known as a physical property value database that stores a molar volume calculation parameter based on a component composition obtained from an experiment in which the molar volume of each phase is linked to a thermodynamic model.

In the material property value calculation step S25, the interaction coefficient obtained from the experiment is introduced and calculated based on the mixing side. In the calculation step S26, the material solidification property value, solidification rate, density, heat transfer coefficient, enthalpy, specific heat, latent heat, Viscosity can be obtained by calculation.
As described above, various physical property values can be calculated by using JmatPro (product name) which is physical property value calculation software. Among these, in this embodiment, the solidification rate is mainly determined, and for example, described later. Thus, the solidification rate curve illustrated in FIG. 5 is formulated by data input and calculation. (Coagulation rate curve formulation step: S2)

For example, when calculating using the standard composition of AA3104 alloy, in the composition input column of the initial input screen of JmatPro (trade name), Al: 97.5 mass%, Cu: 0.15 mass%, Fe: 0 The alloy component composition is input as .4 mass%, Mg: 1.2 mass%, Mn: 1.0 mass%, and Si: 0.2 mass%.
For the solidification rate, segregation is calculated thermodynamically using the Scheil equation (assuming that the liquid phase is fully diffused and the solid phase is not diffused). In the initial input screen of JmatPro (product name), set the start temperature to 700 ° C (temperature above the solidification start point), set the step in 1 ° C increments, select the Phase all item Take all solid phases into account, and click Extend. You can start the calculation by selecting Calculation strength and dendrite arm spacing in the calculation item and pressing the Start caluculation button.

Sheil's equation is known as the following equations (2) and (3). Note that in (2) and (3), Cs is the composition of the solid, _{C 0} is the composition of the original alloy, fs coagulation factor, k: the equilibrium distribution _coefficient, T L, _{T f:} the equilibrium liquid phase Line, solidus temperature is shown.

  JmatPro (trade name) calculates the solidification rate of the Al alloy having the composition according to steps S21 to S26 according to the input contents of the alloy components described above.

FIG. 4 shows an example of a prediction device for susceptibility to solidification cracking in which JmatPro (trade name) and software for executing the above-described other steps according to the present application are stored.
The prediction device 12 for susceptibility to solidification cracking in this example is a so-called computer, and mainly includes an input unit 13, a control unit 14, a storage unit 15, and an output unit 16.
The input means 13 is, for example, a keyboard for inputting letters and numbers, and by this, information such as the type and amount of elements contained in the Al alloy can be input to the storage means 15 or the control unit 14.
The control unit 14 includes a so-called CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and the like, and performs various numerical calculations, information processing, device control, and the like by a program. Can do.

The storage means 15 is an information recording medium such as an HDD (Hard Disk Drive) or SSD (Solid State Drive), for example, and is necessary for executing the program such as the above-mentioned JmatPro (trade name), the calculation means 17 and the prediction means 18. For example, the solidification rate curve based on the composition of the Al alloy, the formulation information of the first position and the second position, which will be described later, the formulation information of the straight line connecting the first position and the second position, the straight line and the solidification rate Various information such as the calculation of the area S of the region surrounded by the curve and the results thereof, the results obtained by these, and the like can be stored and read as necessary.
The output means 14 is, for example, a monitor or a printer. In addition to various information obtained from a program such as JmatPro (trade name), the output means 14 is a graph of the relationship between the coagulation rate and temperature, the coagulation rate, the temperature change amount, and the strain described later. Information such as the speed difference relationship can be displayed or printed on the screen or paper as necessary.

  The storage unit 15 stores in advance various programs necessary for execution of the calculation unit 17 and the prediction unit 18 described later, such as the above-described JmatPro (product name), before executing the program. These can be read and manipulated arbitrarily. In addition, calculation results obtained by executing the program can be stored or read as necessary. Note that the storage means 15 has only the function of communicating with the Internet or a network, and uses the storage means, calculation means, and prediction means provided in other personal computers connected to the Internet or the network, in the same manner as the prediction device 12. Of course, it may be configured so that the result can be calculated.

When the composition of the AA3104 alloy described above is input, JmatPro (trade name) calculates the solidification rate of the Al alloy of the corresponding composition in accordance with steps S21 to S26 and formulates the solidification rate curve. An example solidification rate curve can be displayed on a monitor screen or printed on paper by a printer. JmatPro (trade name) can also calculate the density, heat transfer coefficient, enthalpy, specific heat, latent heat, viscosity, etc. of the Al alloy whose composition is input as required.
Moreover, based on the solidification rate curve obtained from JmatPro (trade name), the solidification rate change per temperature change is output as shown in FIG. 6, and the strain per temperature change is determined from the slope of the graph shown in FIG. Can be requested.

For example, assuming that the range of the solidification rate 0 to 0.75 is the region I shown in FIG. 6, the range of 0.75 to 0.95 is the region II, and the range of 0.95 to 1.0 is the region III. Assuming that the temperature at 0.75 is T ₁ , the slope of the curve at solidification rate 0.75 is R ₁ , the temperature at solidification rate 0.95 is T ₂ , and the slope of the curve at solidification rate 0.95 is R ₂ , the strain The speed difference (ΔR _II / ΔT _II ) has the relationship of the following equation (4). However, ΔT _II = T ₁ −T ₂ as shown in FIG. Since ΔT represents the temperature change amount, ΔT _II means the temperature change amount in the range of the solidification rate of 0.75 to 0.95 (range II).

  The control unit 14 outputs the calculation result of the solidification rate every 1 ° C. calculated by JmatPro (trade name) as text data, and the spreadsheet software executed by the solidification rate every 1 ° C. being stored in the storage means 15 And has a function of automatically inputting the corresponding column. In addition, the temperature gradient for every 1 ° C is automatically entered by the spreadsheet software in the row next to the row where these values are entered, and the coagulation rate difference from the coagulation rate of 0.75 is entered in the row next to it. Then, a linear y coordinate (y coordinate in the graph of the coagulation rate curve) is input to the horizontal column, and a value obtained by taking a non-linear difference dt is calculated and input to the horizontal column. It is preferable to set an automatic calculation sequence of calculation software.

  FIGS. 9A, 9B, and 9C show a part of the text data that the control unit 14 has displayed on the spreadsheet software. This data corresponds to the data of the alloy from which the solidification rate curve shown in FIG. 5 was obtained. The starting temperature starts from 700 ° C., which is sufficiently higher than the melting point, and the data is released to room temperature. Of these data, FIG. 9A shows a data string from 700 to 682 ° C., FIG. 9B shows a data string from 655 to 625 ° C., and FIG. 9C shows from 558 to 548 ° C. Shows the data string. FIG. 9D shows the values of T1, T2, R1, and R2, the calculated values of T1-T2, R1-R2, and the calculation of | R1-R2 | / dt extracted from these data strings by spreadsheet software. Each value was displayed. In FIG. 9E, the heading in the column of the calculated value of | R1-R2 | / dt displays only / dt. Further, the temperature (x), the solidification rate (y) when the solidification rate Fs = 0.75, the temperature (x) when the solidification rate Fs = 0.95, and the solidification rate (y) are displayed. FIG. 9E shows the values of the alloys shown in the examples described later.

With these settings, the temperature range of the coagulation rate 0.75 to 0.95 and the slope of the graph can be automatically calculated.
When performing this automatic calculation, as shown in FIG. 7, there may be an Al alloy exhibiting a solidification rate change gap in a region where the solidification rate is around 0.95. This gap is generated as a singular point of the solidification rate due to precipitation of intermetallic compounds. FIG. 8 is an enlarged view around the singular point of the gap G and the solidification rate.
In the case of an Al alloy showing a singular point in the range of 0.75 to 0.95, the slope of the curve changes greatly before and after the gap. In this case, it is necessary to correct the value so that the slope is just before crystallization. There is. When the control unit 14 confirms such a gap in the range of the solidification rate of 0.75 to 0.95, the control unit 14 corrects the inclination immediately before crystallization. Alternatively, this correction may be performed manually by adopting a value manually. This manual correction will be described in detail in a comparative example described later.
In addition, when calculating with JmatPro (trade name), the temperature increment is set every 1 ° C as described above, but when a new phase appears or disappears, the temperature is continuously calculated as having no increment relationship. It is desirable to do. In that case, the temperature below the decimal point may appear. The result of 552.75 ° C. shown in FIG. 9C means this.
Also, for #VALUE! And # DIV / 0! Shown in FIG. 9A, the solid phase rate or the difference in the solid phase rate is 0, and division by zero has occurred, so values are not calculated. In this example, 8.07134 is output as data at 650 ° C. and the non-linear difference * dt is output from 634 ° C. as data.
Note that 651.02 ° C. shown in FIG. 9B is an extreme point of the start of solidification, and therefore, in this embodiment, the temperature is set to 650 ° C. during normal solidification.

The control unit 14 sets an arbitrary position between the solidification rates of 0.6 to 0.8, for example, a position of 0.75, with respect to the solidification rate curve of each Al alloy calculated and calculated by JmatPro (trade name). It has a function of establishing and grasping the first position and storing it in the storage means 15. Next, with respect to the solidification rate curve, the control unit 14 finishes the crystallization of the primary crystal, and at the position where the gradient of the solidification rate curve shows a discontinuous change point, or if the change point does not occur, the solidification rate Has a function of formulating and grasping the earlier position as the second position when it becomes 0.95 and storing it in the storage means 15 (the specific positions of the first position and the second position are Examples and Comparative Examples and FIG. 9).
Next, the control unit 14 formulates a first position and a second position with respect to the solidification rate curves of the plurality of Al alloys obtained previously, and draws straight lines connecting the first position and the second position. , Each solidification rate curve has a function of calculating an area S of a region surrounded by a straight line and a part of the solidification rate curve.

The area S is an addition of the difference between the function fd indicating the solidification rate according to the thermodynamic database and the function fl indicating the straight line. The fd and fl are functions of the temperature T, and the solidification rate is 0.6 to 0. .8 is T _0.6 to _0.8 , and the temperature at the end of primary crystal crystallization is Te.

For this reason, when obtaining the area S in the range of _{0.75 to 0.95} in the above-described Al alloy, the solution of the above-described formula (1) is obtained as the range of T _{0.75 to} T _0.95. And the area S can be calculated.

Next, the control unit 14 compares the values of the areas S obtained individually for the plurality of Al alloys to be compared, arranges them in order of area, and stores the arranged results and the values of the individual areas S in the storage unit 15. The output unit 16 has a function of outputting to a monitor, a printer or the like and displaying it on a screen or printing on paper (see FIG. 11).
As shown in FIG. 11, the solidification rate curve is compared in the order of the size of the area S according to the type of Al alloy. The larger the area S, the higher the solidification cracking susceptibility, and cracking during casting such as DC casting. It can be grasped that the Al alloy is likely to be generated.
In the example shown in FIG. 11, it can be determined that AA3104 (5Mg) and AA7075 are easy to break, and that AA2024, AA3104 (4Mn), and AA3104 (1Si) are hard to break.
Among these, when casting an Al alloy that is highly susceptible to solidification cracking and is predicted to be easily cracked, it is preferable to cast the corresponding Al alloy under conditions where casting cracks are unlikely to occur.

In the comparison shown in FIG. 11, it can be determined that AA3104 (5Mg) and AA7075 are easily cracked, and that AA2024, AA3104 (4Mn), and AA3104 (1Si) are difficult to crack in the actual casting process known by the present inventor. This is because AA3104 (5Mg) and AA7075 are easily cracked, and AA2024, AA3104 (4Mn), and AA3104 (1Si) are difficult to crack.
For example, when casting under the same conditions of molten metal temperature: 700 ° C., size: width 1200 mm, thickness 600 mm, length 4000 mm, cooling water amount: 2000 L / min, casting speed 50 mm / min, AA3104 (5Mg) and AA7075 are likely to break. , AA2024, AA3104 (4Mn), and AA3104 (1Si) are known to be alloys, although they are difficult to crack.
The composition of AA3104 (5Mg) described in the comparison shown in FIG. 11 corresponds to the composition of alloy 9 of Table 1 shown in the examples described later, and the composition of AA7075 is the composition of alloy 11 of Table 1 shown in the examples described later. Corresponding to the composition, the composition of AA2024 corresponds to the composition of alloy 12 of Table 1 shown in the examples described later, the composition of AA3104 (4Mn) corresponds to the composition of alloy 6 of Table 1 shown in the examples described later, The composition of AA3104 (1Si) corresponds to the composition of Alloy 3 in Table 1 shown in the examples described later.

The solidification crack susceptibility prediction program of this embodiment uses the solidification crack susceptibility prediction device 12 having the configuration shown in FIG. 4 described above, and easily generates cracks during solidification of a plurality of Al alloys according to the above-described composition. This is a program for causing the prediction device 12 to predict the height.
The prediction program for solidification cracking sensitivity uses the prediction device 12 and inputs the composition of the Al alloy to be predicted by the operator into JmatPro (product name). Then, JmatPro (product name: solidification rate curve formulation) according to steps S21 to S26 described above. Means) to draw a coagulation rate curve. FIG. 9 shows an example.
Next, the prediction program for solidification cracking sensitivity uses the prediction device 12 and formulates the first position and the second position in the solidification rate curve according to step S3 described above, draws a straight line connecting them, and sets the solidification rate curve and the straight line. The area S surrounded by is calculated by the area calculation means.
Specifically, the area S is calculated by the calculation means 17 provided in the prediction device 12 according to the above equation (1).

Next, the prediction program for susceptibility to solidification cracks uses the prediction device 12 to compare the plurality of areas S obtained according to the compositions of the plurality of Al alloys to be predicted.
The prediction program for solidification cracking susceptibility has a function of outputting the size of the area S for the Al alloy to be predicted from the output means 16 to a monitor, a printer, or the like, and displaying or printing them in order of increasing area S on the screen or paper. . The display function and the printing function may be displayed in order from the smallest area S, or may be a form in which a specific value of the area S is displayed according to the type of the Al alloy. It may be in the form of displaying with a corresponding large or small figure.
FIG. 11 shows an example in which the type of Al alloy and the value of the area S are displayed in the size of the figure. The example shown in FIG. 11 is an example in which a part of a solidification rate curve for determining the area S and a straight line are graphically displayed in the same order as they are, and the operator should predict by comparing and referring to these figures. It can be recognized by comparing with the Al alloy that compares the ease of solidification cracking of the Al alloy.

By the way, in the above-described embodiment, JmatPro (trade name) is used as the physical property value calculation software for obtaining the coagulation rate curve. However, the physical property value calculation software to be used is not limited to JmatPro (trade name), such as a thermocalc. Software using a general-purpose thermodynamic database may be used. In addition, the method for obtaining the solidification rate curve is not limited to software, and the result of thermal analysis using a differential scanning calorimeter (DSC) or the solidification rate curve obtained in the process of casting using an actual Al alloy is used. Also good.
Any solidification curve obtained by any of these methods can be applied when the method of the present invention is carried out.

Based on the desired range of the content of each element described above, solidification rate curves were obtained for a plurality of Al alloys using JmatPro (trade name: Ver 9.1).
For the solidification rate, segregation was set as a condition for thermodynamic calculation by Scheil's formula (assuming that the liquid phase is completely diffused and the solid phase is not diffused). In the initial input screen of JmatPro (product name), set the start temperature to 700 ° C (temperature above the solidification start point), set the step in 1 ° C increments, select the Phase all item Take all solid phases into account, and click Extend. The calculation item Calculation strength and dendrite arm spacing was selected, and the calculation was started by pressing the Start calculation button.

  In Table 1, for each of the alloys 1 to 12, typical element contents in each alloy composition shown in Table 1 are described after AA3104 so that the relationship with the composition of the AA3104 alloy can be easily understood ( ) And will be described below while distinguishing each alloy. For the content of typical elements, numerical values indicated in bold in the composition shown in Table 1 were adopted. Since alloy 9 in Table 1 contains 5% by mass of Mg, it should be indicated as a 5000-based alloy rather than as a 3000-based alloy. In this example, it is indicated as AA3104 (5Mg). ing.

The example of the calculation result of the solidification rate curve by JmatPro (brand name) of these alloy samples is collectively shown in FIG. With respect to the obtained solidification rate curve, the position of 0.75 is established as the first position as shown in FIG. 10, and the transition point where the gradient is discontinuous in the solidification rate curve after the crystallization of the primary crystal is completed. The position shown or the earlier position when the coagulation rate is 0.95 when the change point does not occur was established as the second position.
Next, a straight line connecting the first position and the second position was drawn on the solidification rate curve, and the area S of the region surrounded by this straight line and a part of the solidification rate curve was calculated.
The area S is calculated by adding the difference between the function fd indicating the solidification rate and the function fl indicating the straight line according to the above equation (1), and calculating the position of the solidification rate 0.75 in each solidification rate curve (first 2) to the second position of each coagulation rate curve.
The above calculation results are shown in Table 2 below.
In this example, since the value of the area S was distributed in the range of 0.10 to 2.79, an intermediate value of 1.5 was used as a standard index as to whether it was easy to break or hard to break.
Further, assuming that the cracking rate of the A3104 alloy (alloy 1) was 1, the cracking rate of each Al alloy was displayed in relative terms.

In the solidification rate curve shown in FIG. 10, the solidification rate curve of AA3104 (4Mn): (Sample No. 6 in Table 1) has two changing points, but the crystallization of the primary crystal is the solidification at the first changing point. Since the rate is 0.95, the position is defined as the second position.
In addition, the same calculation was performed on the Al alloy having the composition shown in Table 3 to obtain the results shown in Table 4.

As for the cracking rate of each alloy sample shown in Tables 2 and 4, the cracking rate of A3104 (1): (No. 1 sample in Table 1) is assumed to be 1, and the cracking rate of each Al alloy sample is displayed in relative terms. .
The crack rates in Tables 2 and 4 are as follows: molten metal temperature: 700 ° C., size: width 1200 mm, thickness 600 mm, length 4000 mm, cooling water amount: 2000 L / min, casting speed 50 mm / min. The crack rate of each alloy is shown.

Next, for comparison, the text data of the coagulation rate for every 1 ° C., which is extracted from the previously determined coagulation rate curve, is displayed in the spreadsheet software recorded in the storage means 15, and the coagulation rate 0.75-0. The slope of the 95 temperature range graph was automatically calculated. Further, the relationship between ΔT _II obtained from the solidification rate curve of each Al alloy and the strain rate difference was obtained.
In order to obtain these relationships, the numerical sequences shown in FIGS. 9A to 9C are automatically input to the spreadsheet software, and T1, T2, R1, and R2 are extracted as shown in FIG. 9D, It can be obtained by calculating the values of T1-T2, R1-R2, | R1-R2 | / dt.

FIG. 12 shows the results of plotting the relationship between the value of the strain rate difference (ΔR _II / ΔT _II ) of each alloy and ΔT _II, and FIG. 13 shows the case of an alloy having a gap due to a singular point in the strain rate difference of each alloy. Shows the result of the above correction.
Of the various Al alloys shown in FIG. 12, the samples AA3104 (1Si), AA3104 (2Mg), and AA3104 (2.8Si) all have singular points, and the value of the strain rate difference is too small. went.
This correction looks at the phase change during solidification, and if there is a point where the temperature becomes almost constant due to the development of the eutectic phase at the end of solidification, if that point is before the solid phase ratio of 0.95, that point Was corrected as a value to replace the solid phase ratio of 0.95.

The value of the strain rate difference (ΔR _II / ΔT _II ) is the strain difference between the solidification rates of 0.75 and 0.95 at an arbitrary moment, that is, the strain rate difference. It is a value grasped by the prior art described in Patent Document 1.
12 and 13, the composition ratio of each alloy used for the calculation is as shown in Tables 1 and 3.

The results shown in FIG. 13 indicate that, under the same casting conditions, the alloy described in the upper right side of FIG. It is an alloy.
10 and 11, among the AA2024, AA7075, and AA3104 (5Mg) derived from the results shown in FIG. 10 and FIG. In the results shown, there was a tendency that AA3104 (5Mg) was easily cracked, but AA3104 (4Mn) was determined to be easily cracked based on the result shown in FIG.
However, this AA3104 (4Mn) is an alloy that is evaluated to be difficult to crack when the inventor actually casts it at the manufacturing site.
AA3104 (1Si) has the same result that the prediction result of the present embodiment shown in FIGS. 10 and 11 and the prediction result by the prior art shown in FIG.

  The prediction result shown in FIG. 13 corresponds to the prediction result obtained by adding the correction result manually performed by the present inventor to the prior art described in Non-Patent Document 1, but previously shown in FIGS. It was found that the prediction result of crack susceptibility obtained from the relationship shown is closer to the state of actual Al alloy casting, and more accurate prediction can be obtained.

  According to the present invention, it is possible to provide a method, an apparatus, and a program capable of predicting the susceptibility to solidification cracking with a higher accuracy than ever even with an Al alloy having a new composition.

  DESCRIPTION OF SYMBOLS 1 ... DC casting apparatus, 2 ... Molten metal, 3 ... Lounder, 5 ... Nozzle, 6 ... Mold, 6a ... Discharge part, 7 ... Bottom block, 8 ... Cooling water, 9 ... Ingot, 10 ... Molten metal pool.

Claims (12)

A method for predicting the ease of occurrence of cracks during solidification of a plurality of Al alloys depending on the composition,
Using the composition of the Al alloy to be predicted, obtaining a phase change for each temperature from the liquid phase to the solid phase, a solidification rate curve formulation step for obtaining a solidification rate curve indicating the relationship between the obtained temperature and the solidification rate,
In the solidification rate curve, an arbitrary first position is established within the solidification rate of the Al alloy within the range of 0.6 to 0.8, and the crystallization of the primary crystal is completed, and the gradient of the solidification rate curve has the gradient. The position indicating the discontinuous change point, or if the change point does not occur, the earlier position when the coagulation rate becomes 0.95 is determined as the second position, and the first position and the second position are determined. An area calculating step for obtaining an area S of a region surrounded by the straight line and the solidification rate curve obtained earlier;
A judgment step of judging that the Al alloy having the larger area S is more likely to cause solidification cracks by comparing the plurality of areas S determined according to the composition of the plurality of Al alloys to be predicted. A method for predicting the susceptibility to solidification cracking of an Al alloy.   Based on a thermodynamic database showing the relationship between temperature and solid fraction, the solidification curve based on the method of calculating the phase change at each temperature from the liquid phase to the solid phase using the Scheil-Gulliver segregation model for solidification calculation The solidification curve formulation step is performed based on a differential thermal analysis result, or the solidification curve formulation step is performed based on a differential thermal analysis result. A method for predicting the susceptibility to solidification cracking of an Al alloy. The area S is an addition of the difference between the function fd indicating the solidification rate according to the thermodynamic database and the function fl indicating the straight line. The fd and fl are functions of the temperature T, and the solidification rate is 0.6 to 0. The Al alloy according to claim 2, having a relationship of the following formula (1), wherein the temperature at the time of .8 is T _0.6 to _0.8 and the temperature at the end of primary crystal crystallization is Te. Of predicting susceptibility to solidification cracking in steel.

  The Al alloy is, by mass%, Si: 0.0001-3.3%, Fe: 0.0001-2.0%, Cu: 0.0001-10.0%, Mn: 0.0001-10.0. %, Mg: 0.0001 to 10.0%, Cr: 0.0001 to 1.0%, Zn: 0.0001 to 10.0%, Ti: 0.0001 to 1.0%, Ni: 0.00. 0001 to 1.5%, Li: 0.0001 to 5.0%, Zr: 0.0001 to 1.0%, B: 0.0001 to 1.0%, Pb: 0.0001 to 0.5% Bi: 0.0001 to 0.5%, V: 0.0001 to 0.5%, including one or more, the balance being Al and inevitable impurities, the α phase of the Al alloy after solidification Solidification cracking of the Al alloy according to any one of claims 1 to 3, wherein the volume ratio of the Al alloy is 80% or more. Method for predicting susceptibility. An apparatus for predicting the ease of occurrence of cracks during solidification of a plurality of Al alloys according to the composition,
Using the composition of the Al alloy to be predicted, the phase change for each temperature from the liquid phase to the solid phase is obtained, and a solidification rate curve formulation means for obtaining a solidification rate curve indicating the relationship between the obtained temperature and the solidification rate;
In the solidification rate curve, an arbitrary first position is established within the solidification rate of the Al alloy within the range of 0.6 to 0.8, and the crystallization of the primary crystal is completed, and the gradient of the solidification rate curve has the gradient. The position indicating the discontinuous change point, or if the change point does not occur, the earlier position when the coagulation rate becomes 0.95 is determined as the second position, and the first position and the second position are determined. An area calculating means for obtaining an area S of a region surrounded by the straight line and the solidification rate curve obtained previously;
A judgment means is provided for judging that the Al alloy having the larger area S is more likely to cause solidification cracks by comparing the plurality of areas S determined according to the composition of the plurality of Al alloys to be predicted. A prediction device for susceptibility to solidification cracking of an Al alloy.   Based on the thermodynamic database showing the relationship between temperature and solid fraction, the solidification curve formulating means uses the Scheil-Gulliver segregation model for solidification calculation to calculate the phase change at each temperature from the liquid phase to the solid phase. 6. The apparatus for predicting the susceptibility to solidification cracking of an Al alloy according to claim 5, characterized in that the apparatus is a means. The area S is an addition of the difference between the function fd indicating the solidification rate according to the thermodynamic database and the function fl indicating the straight line. The fd and fl are functions of the temperature T, and the solidification rate is 0.6 to 0. The Al alloy according to claim 6, having a relationship of the following formula (1), wherein the temperature at the time of .8 is T _0.6 to _0.8 and the temperature at the end of primary crystal crystallization is Te. Prediction device for susceptibility to solidification cracking.

  The Al alloy is, by mass%, Si: 0.0001-3.3%, Fe: 0.0001-2.0%, Cu: 0.0001-10.0%, Mn: 0.0001-10.0. %, Mg: 0.0001 to 10.0%, Cr: 0.0001 to 1.0%, Zn: 0.0001 to 10.0%, Ti: 0.0001 to 1.0%, Ni: 0.00. 0001 to 1.5%, Li: 0.0001 to 5.0%, Zr: 0.0001 to 1.0%, B: 0.0001 to 1.0%, Pb: 0.0001 to 0.5% Bi: 0.0001 to 0.5%, V: 0.0001 to 0.5%, including one or more, the balance being Al and inevitable impurities, the α phase of the Al alloy after solidification The volume fraction of Al is 80% or more, The solidification cracking of the Al alloy according to any one of claims 5 to 7, Predictor of susceptibility. A program for predicting the ease of occurrence of cracks during solidification of a plurality of Al alloys depending on the composition, comprising:
Using the composition of the Al alloy to be predicted, the phase change for each temperature from the liquid phase to the solid phase is obtained, and a solidification rate curve formulation means for obtaining a solidification rate curve indicating the relationship between the obtained temperature and the solidification rate;
In the solidification rate curve, an arbitrary first position is established within the solidification rate of the Al alloy within the range of 0.6 to 0.8, and the crystallization of the primary crystal is completed, and the gradient of the solidification rate curve has the gradient. The position indicating the discontinuous change point, or if the change point does not occur, the earlier position when the coagulation rate becomes 0.95 is determined as the second position, and the first position and the second position are determined. An area calculating means for obtaining an area S of a region surrounded by the straight line and the solidification rate curve obtained previously;
It is made to function as a judgment means for judging that the Al alloy having the larger area S is likely to cause solidification cracks, by comparing the plurality of areas S obtained according to the composition of the plurality of Al alloys to be predicted. Prediction program for susceptibility to solidification cracking of Al alloy.   Based on the thermodynamic database showing the relationship between temperature and solid fraction, the solidification curve formulating means uses the Scheil-Gulliver segregation model for solidification calculation to calculate the phase change at each temperature from the liquid phase to the solid phase. The prediction program for susceptibility to solidification cracking of an Al alloy according to claim 9, characterized in that the program is a means. The area S is an addition of the difference between the function fd indicating the solidification rate according to the thermodynamic database and the function fl indicating the straight line. The fd and fl are functions of the temperature T, and the solidification rate is 0.6 to 0. The Al alloy according to claim 10 having a relationship of the following formula (1), wherein the temperature at the time of .8 is T _0.6 to _0.8 and the temperature at the end of primary crystal crystallization is Te. Prediction program for susceptibility to solidification cracking.

  The Al alloy is, by mass%, Si: 0.0001-3.3%, Fe: 0.0001-2.0%, Cu: 0.0001-10.0%, Mn: 0.0001-10.0. %, Mg: 0.0001 to 10.0%, Cr: 0.0001 to 1.0%, Zn: 0.0001 to 10.0%, Ti: 0.0001 to 1.0%, Ni: 0.00. 0001 to 1.5%, Li: 0.0001 to 5.0%, Zr: 0.0001 to 1.0%, B: 0.0001 to 1.0%, Pb: 0.0001 to 0.5% Bi: 0.0001 to 0.5%, V: 0.0001 to 0.5%, including one or more, the balance being Al and inevitable impurities, the α phase of the Al alloy after solidification The Al alloy according to claim 10 or 11, which is applied to an Al alloy having a volume fraction of 80% or more. Prediction program of the solidification cracking susceptibility.

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